In accordance with prior art, liquid can be atomized into small droplets by a plurality of different techniques, such as with a gas-dispersing atomizer, a pressure-dispersing atomizer and an ultrasound atomizer.
It is known in the prior art that two atomizers can be arranged to be oriented substantially directly towards one another in a manner making the aerosol jets produced thereby collide directly into each other. By orienting the aerosol jets preferably substantially directly against each other, aerosol is produced, which has a negligible net momentum due to direct collision. In other words, in prior art collision based atomizers, as the aerosol becomes substantially stationary, it can be moved in the desired direction with a separate gas flow which is oriented substantially to the collision point of the aerosol jets. The aerosol is used for coating a substrate in a deposition chamber.
While the substrate to be coated is usually arranged in the bottom of the deposition chamber, the atomizers are arranged in a horizontal direction such that the separate gas flow is arranged to discharge gas substantially in a vertical direction to direct the aerosol downwards towards the substrate. The atomizers are typically arranged in pairs for constituting one or more atomizer pairs in such a manner that the atomizers of each atomizer pair are oriented substantially directly coaxially towards each other, whereby the aerosol jets of each atomizer pair collide directly into each other. The atomizer pairs are further arranged in the device in succession or adjacently vertically or horizontally. The idea is that the separate gas flow is substantially toward the collision point of the aerosol jets and substantially toward the substrate to be coated such that the aerosol is directed toward the substrate which means that the atomizers are substantially parallel with the substrate to be coated. With the help of the separate gas flow the aerosol can be shaped into a line-like aerosol front for assisting the coating of the substrate.
One of the disadvantages associated with the above arrangement is that the aerosol directed with the help of the separate gas flow may not be uniform when contacting the substrate. The prior art arrangement requires anyway a separate gas nozzle for dispersing the aerosol with the help of gas flow and every additional component increases costs. Aerosol produced with above mentioned atomizers comprise large droplets and large droplets reduce uniformity and evenness in the coating, so a thick liquid film is required which has a high surface tension and requires long time for becoming even on the surface of the substrate. Aerosol sprays that produce aerosol do not produce uniform aerosol and the aerosol beam is not homogeneous. This is compensated by moving either the spray or object to be coated or by moving both which is quite complicated.